A process for manufacturing semiconductor devices includes performing a predetermined liquid processing by supplying a processing liquid such as a chemical liquid to a substrate such as a semiconductor wafer. Such a liquid processing is performed, for example, by a substrate liquid processing apparatus including a spin chuck configured to hold the substrate in a horizontal posture and rotate the substrate around a vertical axis, a processing liquid nozzle configured to supply the processing liquid to the substrate held by the spin chuck, and a liquid receiving cup configured to receive and recover the processing liquid scattered outwardly from the substrate by a centrifugal force. The liquid receiving cup is provided with an exhaust port, and the exhaust port is connected to an exhaust duct of a factory exhaust system. Since the inside of the exhaust duct is at negative pressure, the internal atmosphere of the liquid receiving cup is exhausted through the exhaust port, and thus, the inside of the liquid receiving cup comes to negative pressure. Meanwhile, since a clean gas flows into the housing, in which the spin chuck and the liquid receiving cup are stored, to form a down flow, the inside of the housing comes to positive pressure with respect to the liquid receiving cup. By forming such a pressure gradient, the atmosphere in a space above the substrate held by the spin chuck (clean gas atmosphere) flows into the liquid receiving cup and is exhausted from the exhaust port of the liquid receiving cup to the factory exhaust system. Since the mist-like processing liquid entrained in the air flow and scattered from the substrate flows smoothly inside the liquid receiving cup towards the exhaust port, re-adhesion of the mist to the substrate is prevented or suppressed.
However, if the pressure relationship is lost for any reason, the air flow accompanied with mist may flow backward to the upper space of the wafer from the inside of the liquid receiving cup. The mist contaminates the surface of the substrate, and adversely affects process results. Accordingly, in order to prevent the contaminated wafer from proceeding in the next process, or in order to take measures of the backward flow, an operation must be able to determine that it is a situation in which backward flow may occur.
Japanese Patent Laid-Open Publication No. 2009-059795 discloses an air flow control technique in which pressure inside a liquid receiving cup is detected by an internal pressure sensor, pressure outside the liquid receiving cup (i.e., pressure in a housing) is detected by an external pressure sensor, and an air flow control device (specifically, a height position of a spin chuck of an air flow control drum with respect to a base) is feedback-controlled such that a value detected by the external pressure sensor is not less than a value detected by the internal pressure sensor. That is, in this case, the pressure gradient is adjusted appropriately by an adjustment mechanism.
In a multi-stage liquid receiving cup having a plurality of cup bodies, different exhaust flow paths are used depending on the kind of the processing liquid supplied to the substrate. Therefore, it is necessary to provide a pressure sensor in each of the exhaust flow paths. However, since the cup bodies constituting the multi-stage liquid receiving cup move for switching the exhaust flow paths, it is difficult to attach the sensor to each of the exhaust flow paths, or a sensor attachment structure becomes complicated.